Project Summary: The biological and environmental impacts of nanoparticles have been a great health concern for decades. It is paramount for our well-being to evaluate the fundamental aspects of the biological interactions of nanoparticles with cells and tissues. There is a gradual increase in the number of reports on neurological clinical complications such as sensory disturbances (auditory disturbances and visual loss), polyneuropathy and hypothyroidism, cardiomyopathy etc., associated with degradation products (DPs) from Total Joint Replacements (TJRs). The recent reports on polyneuropathy associated with CoCr nanoparticles highlight the importance of a mechanistic evaluation of their interaction with neural cells, in the case of total hip replacement (THR). In fact, the generated DPs from the implants are not just metal particles/debris alone, they may present as metal- protein complexes, free metallic ions, inorganic metal salts/oxides and organic storage forms such as hemosiderin. In addition, the bioactivity will vary significantly based on their physicochemical characteristics. Unfortunately, these issues were not addressed in most of the previous investigations. The primary reason for this knowledge gap is the limitations in simulating in vitro experimental set-up to maintain the physiological environment. The central hypothesis of this study is that the complex metal DPs may have significant role in inducing neurodegeneration. The complex form of DPs generated from hip simulator will be the potent in vitro model to study the implant mediated neurotoxicity and neurodegeneration in comparison to that of processed DP as well as single type of metal ions. Hence, the proposed work has a high clinical significance, as our primary goal is to determine the mechanisms by which physiologically relevant CoCr wear nanoparticles cause neuronal dysfunction. With the support of strong preliminary data, the hypothesis will be tested by pursuing two specific aims: Aim 1: To evaluate the physico-chemical characteristics of DPs: We hypothesize that the DPs generated from the hip simulator will have physico-chemical characteristics different from commercially available processed wear particles. This aim will address the generation and characterization of physico-chemical characteristic of DPs from the hip simulator to that of commercially available wear particles. Aim 2: To investigate neural cell toxicity under acute and chronic exposure of DPs in a dynamic environment using Bioreactor on iPSC derived neural cells: We hypothesize that CoCr DPs will cause genomic and mitochondrial DNA damage along with oxidative stress, which further leads to neurodegeneration and may induce peripheral neuropathy. The current aim will address the toxicity of DPs to iPSC derived neural cells, by maintaining the dynamic in vivo joint condition. Two sub-aims are: 2a) Evaluation of neural cell response to CoCr nanoparticles through toxicology tools 2b) Evaluation of molecular mechanism including DNA damage and repair mechanisms. Our approach is innovative since it utilizes a continuous flow bioreactor to study the toxicity of freshly generated, non-processed, more closer in vivo analogue - DP, to the primary neurons using iPSCs derived cells instead of classical cell lines. The proposed research work is significant because it will provide key understanding of fundamental mechanisms that underlie the DP induced neurological complications and establish a future translational approach to develop novel treatment strategies to counter the adverse effects on orthopedic patient.